The present invention relates in general to the field of post surgery patient recovery, and is particularly directed to an involuntary cough-based process for determining whether a patient, who has undergone general anesthesia, is at risk for developing aspiration-based pneumonia. This is accomplished by causing the patient to inhale an aerosol chemostimulant that will stimulate a fully functional (recovered) sensory innervation of the patient""s larynx, causing the patient to involuntarily cough. If the patient fails to cough, however, it is inferred that the patient""s involuntary cough reflex is not yet fully functional, and that the patient is at risk of developing aspiration-based pneumonia.
Any patient who is to be given a general anesthetic for a surgical procedure is intubated prior to surgery. Because the anesthetic effectively pharmacologically suppresses brainstem function, inluding a variety of involuntary physiological responses, not the least of which is the ability to cough and clear the upper airway. These brainstem reflexes are suppressed until the anesthetic wears off. Because the tubing that has been inserted into the patient""s airway tends to act like a wickxe2x80x94drawing fluid (e.g., secreted saliva) that may be present in the patient""s mouth into the patient""s airway and lungsxe2x80x94it is critical that the patient""s involuntary cough reflex be fully functional at the time the patient is extubated.
Unfortunately, there is currently no mechanism for accurately determining whether or not the patient""s ability to involuntarily clear the airway has been fully restored. Instead, because each patient""s anesthesia recovery time is different, the standard medical practice is to have a skilled medical practitioner (e.g., anesthesiologist) observe the patient, and then make an xe2x80x98educated guessxe2x80x99 that the patient""s anesthetic state has completely subsided, and that it is xe2x80x98reasonably safexe2x80x99 to extubate the patient, and allow the patient to receive fluids and/or nutrients by mouth. If the patient""s involuntary cough reflex is not yet fully restored, however, the patient is at considerable risk of developing pneumonia, as a result of entry into the airway from the patient""s mouth of what would otherwise be expelled secretion and/or foreign matter that could be a substrate for breeding bacteria.
In addition, even in those cases where a patient has the ability to cough both involuntarily and voluntarily, the condition of the patient (for example in the case of coronary bypass surgery) may be such that it is extremely difficult and/or painful to have the patient cough voluntarily to clear and expel secretions, mucous and the like from the patient""s airway.
In accordance with a first embodiment of the present invention, the potential problem of post surgery aspiration-based pneumonia, discussed above, is readily determined by means of an aerosol-based screening process, that determines the ability of an extubated post-op recovery patient, whose involuntary cough reflex in the larynx have been previously anesthetized (as by the application of a general anesthetic) or compromised by intubation, to cough involuntarily and thereby clear the patient""s airway of secretion and/or foreign matter that could be a substrate for breeding bacteria and cause pneumonia.
For this purpose, the laryngeal cough reflex of the patient is evaluated by introducing (spray-injecting) an aerosol chemostimulant into the patient""s mouth, for the purpose of stimulating irritant similar types of receptors in the patient""s larynx. The aerosol inhalant preferably comprises that described in U.S. Pat. No. 5,678,563, entitled: xe2x80x9cAspiration Screening Process for Assessing Need for Modified Barium Swallow Study,xe2x80x9d the disclosure of which is herein incorporated, comprising a nebulized or aerosol solution of tartaric acid (tartrate) mixed with saline and is delivered by a standard aerosol nebulizer.
Although other receptor specific chemostimulants may be employed, studies involving the inhalation of a tartaric acid reveal that inhalation of twenty percent nebulized tartaric acid will stimulate an involuntary and abrupt xe2x80x98explosivexe2x80x99 cough, one hundred percent of the time in those patients whose laryngeal cough reflexes have fully recovered from the anesthetic and are fully functional. Further, tartaric acid is considered to be safe, does not cause pain or discomfort, and has not been shown to cause bronchoconstriction or complications in asthmatics or smokers when inhaled in an aerosol form.
The tartrate-containing aerosol stimulant may be injected into the patient""s mouth by a respiratory therapist, using a nebulizer for a relatively brief period of time. The patient may be tested a plurality times at respectively different stimulant strengths to determine whether and at what aerosol strength an involuntary cough can be elicited. During each successive stimulant application, the patient receives progressively increasing concentrations of the aerosol for a prescribed period of time by tidal breathing at one minute intervals using successively increasing percentage concentrations.
If the patient involuntarily coughs as a result of the introduction of any concentration of aerosol stimulant, the inhalation cough test is terminated, regardless of the percentage of concentrations used. The patient""s response to the inhalation test is then graded, for example, as a low pneumonia risk (if the patient coughs immediately in response to the initial aerosol spray and the cough appears strong or normal), or as a high pneumonia risk (where the cough appears weak or the patient does not readily cough in response to the initial concentration spray, but requires a more concentrated aerosol application). If the patient fails to cough for any strength of inhaled aerosol stimulant, the inhalation cough test is terminated, and it is determined that anesthetization of the patient""s laryngeal cough reflex has not fully subsided, so that the patient remains at high pneumonia risk and may not be given fluids or nutrients by mouth.
In a second embodiment of the invention, using a procedure termed a xe2x80x9cpulmonary toilet,xe2x80x9d involving repeated applications of the tartaric acid aerosol spray described above, the patient is involuntarily forced to cough multiple times and thereby remove potentially threatening fluid and other matter from the patient""s airway. This second embodiment of the invention is employed where the condition of the patient is such that it is extremely difficult and/or painful to have the patient cough voluntarily to clear and expel secretions, mucous and the like from the patient""s layrnx.